Network System, Management Server System, Control Method, and Storage Medium for Tenant Transition

1. A network system comprising: a management server system that manages a plurality of network devices; and an agent device that is provided in a site network including the plurality of network devices and communicates with the management server system, wherein the management server system comprises: a first processor; and a first memory including first instructions that, when executed by the first processor, cause the first processor to: manage identification information about the agent device and current authentication information for communication between the management server system and the agent device by associating the identification information and the current authentication information with a first tenant; accept a transition instruction for transition from the first tenant to a second tenant of the agent device; generate symmetric keys including a first key and a second key in accordance with the accepted transition instruction, wherein information, including the generated first key and the identification information about the agent device, is managed in association with the second tenant serving as a transition destination; transmit, in response to a query from the agent device, a response including information about the second tenant serving as the transition destination and the generated second key; upon reception of a transition request for transition to the second tenant, verify first signature information included in the transition request using the first key which is managed in association with the second tenant; upon successful verification of the first signature information, transmit, to the agent device, new authentication information for communication between the management server system and the agent device; delete the identification information about the agent device and the current authentication information associated with the first tenant in response to receipt of a successful transition notification from the agent device, and wherein the agent device comprises: a second processor; and a second memory including second instructions that, when executed by the second processor, cause the second processor to: send the query to the management server system; receive the response based on the query; and transmit, to the management server system, a transition request for transition to the second tenant, the transition request including second signature information using the second key included in the response.

2. The network system according to claim 1 , wherein the first instructions, when executed by the first processor, further cause the first processor to encrypt the new authentication information using the first key, and then transmit the encrypted new authentication information to the agent device.

3. The network system according to claim 1 , wherein the first instructions, when executed by the first processor, further cause the first processor to generate the symmetric keys with an expiration date.

4. The network system according to claim 1 , wherein the second instructions, when executed by the second processor, further cause the second processor to judge whether or not the agent device is capable of communicating with the management server system using the new authentication information.

5. The network system according to claim 1 , wherein the first instructions, when executed by the first processor, further cause the first processor to, upon successful verification of the second signature information, associate the identification information about the agent device and the new authentication information generated for the agent device with the second tenant.

6. The network system according to claim 1 , wherein the second instructions, when executed by the second processor, further cause the second processor to store, in association with the second tenant, new authentication information that has been transmitted from the management server system in accordance with successful verification of the second signature information.

7. The network system according to claim 6 , wherein the second instructions, when executed by the second processor, further cause the second processor to decrypt the new authentication information encrypted and transmitted to the agent device using the second key included in the response, and then store the decrypted new authentication information.

8. The network system according to claim 1 , wherein the first instructions, when executed by the first processor, further cause the first processor to determine a date and time at which transition is performed after reception of the successful transition notification from all the agent devices.

9. The network system according to claim 8 , wherein the second instructions, when executed by the second processor, further cause the second processor to perform a transition to the second tenant by acquiring the determined date and time, and communication between the agent device which has been transitioned to the second tenant and the management server system is performed using the new authentication information.

10. A management server system that manages a plurality of network devices via an agent device which is provided in a site network including the plurality of network devices, the management server system comprising: a processor; and a memory storing instructions that, when executed by the processor, cause the processor to: manage identification information about the agent device and current authentication information for communication between the management server system and the agent device by associating the identification information and the current authentication information with a first tenant; accept a transition instruction for transition from the first tenant to a second tenant of the agent device; generate symmetric keys including a first key and a second key in accordance with the accepted transition instruction, wherein information, including the generated first key and the identification information about the agent device, is managed in association with the second tenant serving as a transition destination; transmit, in response to a query from the agent device, a response including information about the second tenant serving as the transition destination and the generated second key; upon reception of a transition request for transition to the second tenant, verify signature information included in the transition request using the first key which is managed in association with the second tenant; upon successful verification of the signature information, transmit, to the agent device, new authentication information for communication between the management server system and the agent device; and delete the identification information about the agent device and the current authentication information associated with the first tenant in response to receipt of a successful transition notification from the agent device, wherein communication between the management server system and the agent device which has been transitioned to the second tenant is performed using the new authentication information.

11. A non-transitory computer-readable storage medium having stored thereon a computer program that, when executed by a processor, causes the processor to function as the management server system according to claim 10 .

12. A control method for controlling a management server system that manages a plurality of network devices via an agent device which is provided in a site network including the plurality of network devices, the control method comprising: managing identification information about the agent device and current authentication information for communication between the management server system and the agent device by associating the identification information and the current authentication information with a first tenant; accepting a transition instruction for transition from the first tenant to a second tenant of the agent device; generating symmetric keys including a first key and a second key in accordance with the accepted transition instruction, wherein information, including the generated first key and the identification information about the agent device, is managed in association with the second tenant serving as a transition destination; transmitting, in response to a query from the agent device, a response including information about the second tenant serving as the transition destination and the generated second key; verifying, upon reception of a transition request for transition to the second tenant, signature information included in the transition request using the first key which is managed in association with the second tenant; transmitting to the agent device, upon successful verification of the signature information, new authentication information for communication between the management server system and the agent device; and deleting the identification information about the agent device and the current authentication information associated with the first tenant in response to receipt of a successful transition notification from the agent device, wherein communication between the management server system and the agent device which has been transitioned to the second tenant is performed using the new authentication information.